Evaporative cooling equipment is instruments that put an air stream in contact with a water stream to reduce the air temperature, taking advantage of the energy absorbed by the water in its evaporation process. It is a process that occurs in nature in areas with abundant vegetation, the water filtered from the roots evaporates in the leaves and gives a feeling of freshness. The natural body cooling system is also based on this principle, the evaporation of sweat water causes a decrease in body temperature.
What has been your technical evolution?
Evaporative conditioning has been the first form of air conditioning used by humans, it is known that in the ancient Greek and Roman civilizations bales of wet straw placed in the windows were used to decrease the temperature of the rooms. The Arabs learned from the Persians the management of the fountains to reduce the temperature of the shaded patios that in turn are part of the classical architecture of southern Spain. From 1920, with the beginning of the use of electric power, fans and soaked sheets were used to decrease the room air temperature, in desert areas of Arizona (USA). These concepts have now been refined giving rise to evaporative air conditioning equipment.
How can we describe its operation?
The operation of these devices is based on the partial evaporation of water in direct contact with the air flow. With this phenomenon, two effects are achieved, cooling the air and humidifying it. The main objective in this equipment is normally refrigeration. Other equipment that sprays water on an air stream in order to humidify it, is usually used in various uses of ventilation and air conditioning, but these humidifiers or humidifiers are not evaporative cooling equipment.
There are several types of evaporative cooling facilities. From the point of view of water use we can consider a first classification:
- Equipment without water recirculation (lost water)
- Equipment with water recirculation
Considering the way in which the system puts water in contact with air, we should consider two types of systems:
- Contact with wet surface by spilled water
- Water sprayed through nozzles
Equipment with water recirculation and contact with wet surface
These equipments are constituted by a housing on whose walls there are panels of porous material (filling), usually treated wood chips, cellulose or in the most sophisticated equipment, fiberglass panels. The base of the equipment acts as a storage raft of a small amount of water that constantly recirculates by means of a pump that pours the water on the porous material of the walls and picks it up again from the raft.
Inside the housing there is a fan whose suction effect drives the warm outside air through the soaked porous panels, evaporating a certain amount of water and getting a slight cooling of the air that finally enters the area to be heated. The evaporated water reduces the amount of circulating water in the equipment and this is replenished by a buoy system and water tap renewal.
Lost water equipment sprayed by nozzles
These are water spray systems equipped with medium or high pressure pumps and a tube system with nozzles that generate micro drops of up to 5μ, directly in the areas where you want to achieve the cooling effect or sometimes even an effect aesthetic type, or both simultaneously. From a Legionella transmission point of view, these devices pose a significant risk, since the distance between people and the spray point is very small and the droplet size is very small. In their favor they have the fact that the working temperatures are normal for the supply network, and therefore in principle they are not usually very high, there is no water recirculation.
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